The investigation of the origins of, and control mechanisms governing spermatozoan motility will employ electron microscopic cytochemistry, radioautography and electrophysiologic procedures. The rate and pattern of motility following treatment of the sperm cells with neurotransmitter and specific pharmacologic inhibitory substances will be determined by a quantitative centrifugation-orientation technique and by stroboscopic analysis. The ultimate objective is to examine the relationships between the fine structure and the regulatory processes which normally modify the contractile activity of the sperm cell flagellum during its development and when mature. With this information at our disposal we aim to deliberately control sperm cell transport and fertilizing capacity in a predictable and reproducible fashion.